1. Field of the Invention
This invention relates generally to apparatus for indicating the presence of sounds and more particularly, but not by way of limitation, to apparatus for indicating both the time of day and the relative level of sound intensity present in the environment of the apparatus.
2. Description of the Prior Art (Prior Art Statement)
The following statement is intended to be a Prior Art Statement in compliance with the guidance and requirements of 37 C.F.R. SS1.56, 1.97 and 1.98.
U.S. Pat. No. 2,982,914 issued to Stewart discloses a noise meter proposed to include a microphone, amplifiers, a rectifier, an integrator, and an indicator. This proposal is directed to indicating a measurement which is proportional to the hazardous effects of a noisy environment.
U.S. Pat. No. 3,802,535 issued to Peake et al. discloses an acoustic noise exposure meter which is proposed to detect sound intensity levels above 90 dB. The device is proposed to include a receiver, an AC-to-DC converter, a voltage-controlled oscillator, a noise threshold comparator, and a counter for displaying a measurement representing total noise to which a person has been exposed.
U.S. Pat. No. 3,747,703 issued to Knowd et al. discloses a noise exposure computer and method which are proposed to indicate cumulative noise exposure. This patent indicates the use of operational amplifiers in the circuits of the proposed device. Another patent disclosing the use of operational amplifiers in sound indicators is U.S. Pat. No. 3,545,564 issued to Barber.
In addition to the above patents, Applicant knows of the following patents which also disclose sound level indicators:
______________________________________ Patent No. Inventor ______________________________________ 2,590,460 Rackey et al. 2,884,085 Von Wittern et al. 3,089,561 Michael et al. 3,236,327 Church et al. 3,615,162 Barber 3,848,471 Hamburg et al. ______________________________________
Applicant believes that these patents are generally directed to apparatus for detecting high sound levels, or "noise". Specifically, the following patents known to Applicant are directed to noise pollution hazards and the Walsh-Healey law noise criteria:
______________________________________ 3,696,206 Ida et al. 3,778,552 Edinborgh 3,868,857 Maddox et al. 3,884,086 Steger 3,977,257 Steger ______________________________________
Other noise exposure meter patents known to Applicant are U.S. Pat. No. 3,014,550 issued to Gales et al. and U.S. Pat. No. 3,144,089 issued to Lane et al. which propose the use of electrochemical integrator units in their indicators.
As shown by the above-mentioned disclosures, there is a need for an apparatus which indicates levels of sound. Applicant believes that these prior proposals have been directed to protecting people who have normal hearing by indicating to them the presence of continuous levels of noise (i.e., sound intensity levels above approximately 90 dB). However, for people having hearing impediments there is a need for a device which can alert them to the presence of lower levels of sound.
Such a device is needed to indicate the loudness of a user's own voice. A device having this feature would be advantageous to a user who wears a hearing aid by aiding the user in properly setting the sensitivity of the hearing aid.
Such a lower level sound indicator would also be useful in providing an awareness of sound in general. For example, this device would alert the user to conversation or to the ringing of a doorbell. More specifically, such a device would provide a warning of potential hazards by notifying the user of sounds emitted by such things as smoke detectors, fire alarms, car horns and other people.
In order to supply these uses there is a need for such a sound detecting device to detect sound intensities within syllabic time periods instead of long-term time periods. There is also the need for a low level monitor within such device for detecting sound levels which are below the normally detected levels and for detecting high sound levels existing for time periods which are shorter than those normally detected.
Additionally there is a need for such a device to be compact so that it can be conveniently worn by the user. In particular it would be advantageous for such a device to be combined with a wrist-watch. To achieve such a small size there is a further need for the device to consume as little power as possible. Therefore, there is a need for relatively high power consuming elements within the device to be duty-cycled to reduce the drain on the power supply. Still further, to maintain a small size there is a need for a simple means for automatically adjusting offset errors resulting from the intrinsic characteristics of the components of the sound level indicator. By satisfying this need a continuously accurate readout can be maintained while still achieving the compact size.
Although the previously cited prior art known to Applicant discloses various proposals pertaining to sound level indicators, Applicant believes that this prior art fails to disclose, either individually or collectively, the present invention which satisfies the needs stated above.